I agree with the first few posts: it's a myth and you certainly don't need to do it.
I will also offer my own personal experience with both methods: I started out feeding in separate enclosures because I believed everything I had heard about BPs and snakes in general. Always feed in a separate container or they will get aggressive blah blah... I came here (thankfully) and learned a very good lesson: it's totally not true and completely unnecessary!! So I began feeding my snakes in their living spaces (I use Dri Dek or paper substrate so I don't have to worry about them ingesting pieces), and not only has the transition been flawless, but I got one of my problem eaters to come around by feeding him this way and never looked back since.
Hope all our input helps you make the decision that's best for you! :)